Power management apparatus, power management system, and method for power management

ABSTRACT

Remaining power information regarding remaining power generation capability of a power generation apparatus is reported. A power management apparatus (2) includes a communication interface (22) that receives remaining power information regarding remaining power generation capability of a power generation apparatus (10) from a power conversion apparatus (1) and an output interface (23) that outputs the remaining power information.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese Patent Application No. 2013-155940 filed Jul. 26, 2013, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a power management apparatus, a power management system, and a method for power management.

BACKGROUND

In recent years, techniques have become known for using a power management apparatus (for example, a Home Energy Management System (HEMS)) provided for each consumer's facility to control the load established for the consumer's facility, the distributed power source established for the consumer's facility, and the like (see JP 2003-309928 A (PTL 1)).

As the distributed power source, it is thought that a power generation apparatus that generates power from natural energy, such as a photovoltaic power generation apparatus or the like, will be used. The power generation amount during power generation from natural energy can vary for a variety of reasons. In order for the power management apparatus to control other apparatuses, however, it may be necessary to predict the power generation amount. Therefore, it has been proposed to calculate a predicted value of the power generation amount by predicting the solar radiation intensity based on past solar radiation intensity, weather information, and the like and converting the predicted solar radiation intensity into a power generation amount by photovoltaic power generation (see JP 2005-086953 A (PTL 2)).

CITATION LIST Patent Literature

PTL 1: JP 2003-309928 A

PTL 2: JP 2005-086953 A

SUMMARY Technical Problem

Such a power management apparatus, however, does not report remaining power information regarding remaining power generation capability of a power generation apparatus, and the user cannot accurately learn the remaining power information.

It would therefore be helpful to provide a power management apparatus, a power management system, and a method for power management that can report remaining power information regarding remaining power generation capability of a power generation apparatus.

Solution to Problem

In order to solve the aforementioned problem, a power management apparatus according to this disclosure is a power management apparatus capable of communicating with a power conversion apparatus for converting power of a power generation apparatus, the power management apparatus including: a communication interface configured to receive remaining power information regarding remaining power generation capability of the power generation apparatus from the power conversion apparatus; and an output interface configured to output the remaining power information.

In the power management apparatus according to this disclosure, the output interface may cause the remaining power generation capability of the power generation apparatus in a load following mode to be output graphically, power generation being controlled to follow load power in the load following mode.

In the power management apparatus according to this disclosure, the output interface may cause power generation of the power generation apparatus in the load following mode to be output graphically in a different form from the remaining power generation capability.

In the power management apparatus according to this disclosure, the output interface may cause the power generation and the remaining power generation capability of the power generation apparatus in the load following mode to be output graphically as a bar chart or a pie chart representing a composition ratio of the power generation and the remaining power generation capability with respect to maximum power generation.

In the power management apparatus according to this disclosure, the output interface may cause power generation of a power generation apparatus in MPPT mode to be output graphically as a bar chart or a pie chart in which a composition ratio of the power generation with respect to the maximum power generation is 100%, the power generation being controlled to follow a maximum power point in the MPPT mode.

In the power management apparatus according to this disclosure, the output interface may cause an area of the bar chart or the pie chart to be proportional to a magnitude of the maximum power generation.

In the power management apparatus according to this disclosure, a plurality of the power generation apparatuses may be connected in parallel to the power conversion apparatus, and the output interface may cause remaining power generation capability of the plurality of power generation apparatuses in the load following mode to be output graphically.

In the power management apparatus according to this disclosure, the output interface may cause power generation and remaining power generation capability of one of the plurality of power generation apparatuses in the load following mode to be output graphically in different forms.

In the power management apparatus according to this disclosure, when graphically outputting the remaining power generation capability of the plurality of power generation apparatuses as a bar chart, the output interface may set a length of each bar chart to be equivalent and vary a width of each bar chart according to output.

In the power management apparatus according to this disclosure, each of the plurality of power generation apparatuses connected to the power conversion apparatus may be a solar cell string in which a plurality of solar cell modules are connected in series.

In the power management apparatus according to this disclosure, all of the plurality of solar cell modules may have equivalent characteristics.

In order to solve the aforementioned problem, a power management system according to this disclosure is a power management system including: a power conversion apparatus for converting power of a power generation apparatus and supplying the power to a load of a consumer's facility; and a power management apparatus capable of communicating with the power conversion apparatus, such that the power conversion apparatus includes: a controller configured to acquire remaining power generation capability of the power generation apparatus; and a first communication interface configured to transmit remaining power information regarding the remaining power generation capability to the power management apparatus, and the power management apparatus includes: a second communication interface configured to receive remaining power information regarding remaining power generation capability of the power generation apparatus from the power conversion apparatus; and an output interface configured to output the remaining power information.

In order to solve the aforementioned problem, a method for power management according to this disclosure is a method for power management in a power management apparatus capable of communicating with a power conversion apparatus for converting power of a power generation apparatus, the method including: receiving remaining power information regarding remaining power generation capability of the power generation apparatus from the power conversion apparatus; and outputting the remaining power information.

Advantageous Effect

According to this disclosure, remaining power information related to the remaining power generation capability of the power generation apparatus can be reported, and the user can accurately learn the remaining power information.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram illustrating an example of the structure of a power management system according to one of the disclosed embodiments;

FIG. 2 is a block diagram illustrating another example of the structure of a power management system according to one of the disclosed embodiments;

FIG. 3 is a circuit diagram of DC/DC converters in a power conversion apparatus within the power management system according to one of the disclosed embodiments;

FIG. 4 is a block diagram illustrating the function of a controller in the power conversion apparatus within the power management system according to one of the disclosed embodiments;

FIG. 5 is a flowchart illustrating operation of the power conversion apparatus within the power management system according to one of the disclosed embodiments;

FIG. 6 illustrates the current/voltage characteristics of a power generation apparatus;

FIG. 7 illustrates power generation of a power generation apparatus;

FIGS. 8A and 8B illustrate power generation of power generation apparatuses in the case of different amounts of sunlight; and

FIGS. 9A and 9B illustrate an example of remaining power information output by the power management apparatus according to one of the disclosed embodiments.

DETAILED DESCRIPTION

With reference to the drawings, the following describes a disclosed embodiment in detail.

FIG. 1 is a block diagram illustrating an example of the structure of a power management system according to one of the disclosed embodiments. The power management system includes a power conversion apparatus 1 and power management apparatus 2. FIG. 1 also illustrates a plurality of power generation apparatuses (DC input power sources) 10 connected to the power conversion apparatus 1 and AC input devices 3 connected to the power management apparatus 2. The power conversion apparatus (power conditioner) 1 includes a plurality of DC/DC converters (input interfaces) 11, an intermediate link capacitor 12, an inverter 13, a controller 14, and a communication interface 15. Although the output of the power conversion apparatus 1 in FIG. 1 is a single-phase two-wire system, the output format is not limited to this system and may, for example, be a three-phase system.

The power conversion apparatus 1 converts the DC power that is input from the connected plurality of power generation apparatuses 10. The power conversion apparatus 1 normally performs interconnected operation by interconnecting with the power grid and performs independent operation by disconnecting from the grid when a power outage occurs in the power grid. The power conversion apparatus 1 thus supplies power to loads of the consumer's facility.

The power generation apparatus 10 outputs DC power. Each of the plurality of power generation apparatuses 10 is a distributed power source, such as a solar cell string, in which a plurality of solar cell modules that convert sunlight to DC power are connected in series; a wind power generator; a fuel cell; or the like. All of the characteristics of the plurality of solar cell modules are preferably the same, for example as a result of each solar cell module being exactly the same.

The DC/DC converters 11 raise the voltage input from the power generation apparatuses 10 for alignment to a constant voltage. In this embodiment, there are three each of the power generation apparatuses 10 and the DC/DC converters 11, but it suffices for there to be two or more each of the power generation apparatuses 10 and the DC/DC converters 11.

The intermediate link capacitor 12 smooths the DC voltage, which was raised by the DC/DC converter 11, to stabilize the input voltage that is input into the inverter 13. A capacitor for smoothing may be further provided inside each DC/DC converter 11 in order to stabilize the output voltage.

The inverter 13 collectively receives input of the voltage output by the DC/DC converters 11 and converts the DC voltage smoothed by the intermediate link capacitor 12 into AC voltage. The inverter 13 is normally interconnected to the power grid but performs independent operation during a power outage or the like, disconnecting from the power grid and supplying AC power to AC input devices (load devices) 3. FIG. 1 illustrates connection between the power conversion apparatus 1 and AC input devices 3 during independent operation.

The controller 14 controls the output of the DC/DC converters 11 and the inverter 13 by controlling the duty cycle of the switching elements in the DC/DC converters 11 and the inverter 13. During independent operation that is disconnected from the power grid, the controller 14 acquires the remaining power generation capability of the power generation apparatuses 10 by calculation. At this time, the controller 14 performs MPPT control on a priority basis on at least one DC/DC converter 11 and uses the generated current of the power generation apparatus 10 connected to the DC/DC converter 11 to calculate the remaining power generation capability of the power generation apparatuses 10 connected to the other DC/DC converters 11.

The communication interface 15 acquires remaining power information indicating the remaining power generation capability of the power generation apparatuses 10 from the controller 14 and transmits a communication message including the remaining power information to the power management apparatus 2. The communication interface 15 may transmit the remaining power information upon acquiring new remaining power information from the controller 14 or may transmit the remaining power information periodically at predetermined time intervals. Furthermore, the communication interface 15 may, upon receiving a request for remaining power information from the power management apparatus 2, respond by transmitting the remaining power information.

The power management apparatus 2 is a apparatus that controls the operation of load devices connected to the power conversion apparatus 1, and depending on the target of management, may be referred to as a Home Energy Management System (HEMS), Building Energy Management System (BEMS), Factory Energy Management System (FEMS), or Community Energy Management System (CEMS).

The power management apparatus 2 includes a communication interface 22 for communicating with the outside and an output interface 23. The communication interface 22 receives information on remaining power generation capability from the communication interface 15 and outputs the information on remaining power generation capability with the output interface 23. In other words, a method for power management in the power management apparatus 2 includes the steps of receiving remaining power information regarding remaining power generation capability of the power generation apparatus 10 from the power conversion apparatus 1 and outputting the remaining power information. Information on power consumption, such as rating, is acquired from the AC input devices 3. Based on the information on remaining power generation capability and the information on power consumption, the AC input devices 3 are controlled.

The output interface 23 outputs the remaining power information input from the communication interface 22 graphically with a display 24 or as audio with a speaker 25. The display 24 or speaker 25 may be internal to the power management apparatus 2, as illustrated, or may be provided externally. When outputting the remaining power information to the speaker 25, the remaining power information is audio information on the present power generation, the remaining power generation capability, and the like. When the AC input device 3 cannot be activated due to a lack of remaining power generation capability, an alarm may be sounded as the remaining power information. When outputting the remaining power information graphically with the display 24, the output interface 23 causes the remaining power generation capability of a plurality of the power generation apparatuses 10 in a load following mode to be output graphically. The power generation and the remaining power generation capability of each power generation apparatus 10 are preferably output graphically in different forms. A detailed example is described below.

FIG. 2 is a block diagram illustrating another example of the structure of the power conversion apparatus 1. As compared to the power conversion apparatus 1 illustrated in FIG. 1, the power conversion apparatus 1 illustrated in FIG. 2 further includes a DC/DC converter 16 on the output side. The DC/DC converter 16 converts the DC voltage smoothed by the intermediate link capacitor 12 to a predetermined DC voltage and supplies DC power to DC input devices 4 during independent operation. By providing the DC/DC converter 16, DC power can be supplied to the DC input devices 4.

In this way, the power conversion apparatus 1 includes a power converter on the output side. The power converter may be the inverter 13 alone, as illustrated in FIG. 1, or may be the inverter 13 and the DC/DC converter 16 connected in parallel, as illustrated in FIG. 2. Although not illustrated, the power converter may also be the DC/DC converter 16 alone, or may be any number of inverters 13 and DC/DC converters 16 connected in parallel.

FIG. 3 illustrates an example of a circuit diagram of the DC/DC converters 11 in the power conversion apparatus 1. FIG. 3 also illustrates the controller 14 that performs control on the DC/DC converters 11. FIG. 3 illustrates typical non-isolated boost converters, but the specific circuit structure is not limited to this example. Any structure having a function that can change the impedance as viewed from the input power source and that can control each input power independently to be a desired value may be adopted.

The controller 14 monitors the input voltage of each DC/DC converter 11 detected by input voltage sensors 19 (19-1, 19-2, 19-3), the input current of each DC/DC converter 11 detected by input current sensors 20 (20-1, 20-2, 20-3), and the intermediate link voltage of the inverter 13 detected by an intermediate link voltage sensor 21. Based on these values, the controller 14 generates a PWM signal for the switching element 18 (18-1, 18-2, 18-3) of each of the DC/DC converters 11. Details regarding the control performed on the DC/DC converters 11 are provided below.

FIG. 4 is a block diagram illustrating the functions of the controller 14 in the power conversion apparatus 1. Operations of the controller 14 are described with reference to FIG. 4.

A duty cycle controller 141-1 controls the duty cycle used to generate the PWM signal for the DC/DC converter 11-1. Similarly, a duty cycle controller 141-2 controls the duty cycle used to generate the PWM signal for the DC/DC converter 11-2, and a duty cycle controller 141-3 controls the duty cycle used to generate the PWM signal for the DC/DC converter 11-3. The duty cycle controllers 141-2 and 141-3 perform the same control as the duty cycle controller 141-1. Moreover, a block diagram of the internal structure of the duty cycle controllers 141-2 and 141-3 is the same as that of the duty cycle controller 141-1 and therefore is not illustrated.

A control mode determiner 142 determines the control mode to be MPPT control during interconnected operation. During MPPT control, the power generation obtained from the power generation apparatus 10 is controlled so as to be maximized.

If MPPT control is performed on all of the DC/DC converters 11 during independent operation, however, the balance between the power consumption of the AC input devices 3 and the power generation of the power generation apparatuses 10 is lost. If load following control is performed on all of the DC/DC converters 11 during independent operation, the power generation apparatuses 10 cannot generate power at maximum power. During load following control (load following mode), the output voltage of the DC/DC converter 11 is controlled so that the power generation follows the load power, i.e. so that the power consumption of the load and the power generation of the input power source become the same. If the power generation apparatus 10 that is trying to follow the power consumption of the load exceeds the maximum power point, the power generation of that power generation apparatus 10 reduces, causing the other power generation apparatuses 10 to exceed the maximum power point by a chain reaction. Ultimately, operation may be suspended due to a lack of power generation.

Therefore, in accordance with the intermediate link voltage detected by the intermediate link voltage sensor 21 during independent operation, the control mode determiner 142 determines the control mode to be either MPPT control or load following control.

For example, if the maximum power generation of each power generation apparatus 10 is 200 W, and the power consumption of the AC input devices 3 is 500 W, then the DC/DC converters 11-1 and 11-2 are subjected to MPPT control to obtain a power of 400 W, and the DC/DC converter 11-3 is subjected to load following control to obtain the remaining 100 W of power. In this way, the overall power generation of the power generation apparatuses 10 is made to follow the power consumption of the load.

An MPPT controller 143 monitors the input voltage detected by the input voltage sensor 19 and the input current detected by the input current sensor 20. When the control mode is determined to be MPPT control by the control mode determiner 142, the MPPT controller 143 determines the operation voltage that maximizes the input power to the power conversion apparatus 1. Whereas following is based on input voltage in the example illustrated in FIG. 4, the specific form of MPPT control is not limited to this example.

When the control mode is determined to be load following control by the control mode determiner 142, a load following controller 144 determines the operation voltage that causes the intermediate link voltage detected by the intermediate link voltage sensor 21 to become a target voltage.

An input voltage controller 145 compares the input voltage detected by the input voltage sensor 19 with an operation voltage command value that is determined by the MPPT controller 143 or the load following controller 144 and performs feedback control to change the duty cycle so that the difference becomes equivalent to zero. In the example illustrated in FIG. 4, control is performed so that the operation voltage of the input power source becomes the command value, but it suffices for the controller 14 to perform control to switch between MPPT control and load following control based on the intermediate link voltage. Therefore, control may be performed based on the operation current of the input power source (feedback control based on input current).

A PWM unit 147 generates a PWM signal by comparing a reference waveform, which is synchronized with a clock generated by a clock generator 146, with the duty cycle generated by the input voltage controller 145. The PWM unit 147 then outputs the PWM signal to each DC/DC converter 11.

During independent operation that is disconnected from the power grid, a remaining power generation capability calculator 148 uses the generated current of the power generation apparatus 10 connected to the DC/DC converter 11 on which MPPT control is performed to calculate the remaining power generation capability of the power generation apparatuses 10 connected to the other DC/DC converters 11 and outputs remaining power information indicating the remaining power generation capability to the communication interface 15. Details on the calculation method are provided below.

FIG. 5 is a flowchart illustrating operation of the controller 14. When a power outage has not occurred (step S101: No), the controller 14 performs interconnected operation and performs MPPT control on all of the DC/DC converters 11 (step S102).

When a power outage has occurred (step S101: Yes), the controller 14 disconnects from the grid to perform independent operation and performs MPPT control on a priority basis on at least one DC/DC converter 11 (step S103). The reason is described with reference to FIGS. 6 and 7.

FIG. 6 illustrates the current/voltage characteristics when the power generation apparatus 10 is a solar cell string. The horizontal axis represents output voltage, and the vertical axis represents output current. The output voltage of the solar cell string is determined by the number of solar cell modules and the temperature and exhibits little change. On the other hand, the output current of the solar cell string varies greatly due to the amount of sunlight. When the amount of sunlight decreases, the output current reduces. In other words, when the amount of sunlight changes, the maximum power generation depends on the generated current.

FIG. 7 schematically illustrates the voltage and current generated by three power generation apparatuses 10-1, 10-2, and 10-3. In this embodiment, the maximum power generation increases in the order of the power generation apparatus 10-1, power generation apparatus 10-2, and power generation apparatus 10-3. The area of the portion enclosed by the dashed line indicates the maximum power generation during interconnected operation (i.e. during MPPT control), and the area of the hatched portion indicates power generation during independent operation.

The generated voltages V1 _(M), V2 _(M), and V3 _(M) of the power generation apparatuses 10 during MPPT control take different values in accordance with the number of solar cell modules in each power generation apparatus 10. On the other hand, the generated currents I1 _(M), I2 _(M), and I3 _(M) of the power generation apparatuses 10 during MPPT control vary in accordance with the amount of sunlight. Assuming that the amount of sunlight is the same for the power generation apparatuses 10, however, the relationship I1 _(M)=I2 _(M)=I3 _(M) can be assumed. Accordingly, by performing MPPT control on a priority basis on at least one DC/DC converter 11 during independent operation (step S103), the controller 14 can learn what the generated current is when MPPT control is performed on the other DC/DC converters 11.

During independent operation, even when the power consumption of the AC input devices 3 is low, it is thought that the power consumption will exceed the maximum power generation of the power generation apparatus 10-1. Therefore, during independent operation, the controller 14 preferably performs MPPT control on a priority basis on the DC/DC converter 11-1 to which the power generation apparatus 10-1 with the smallest maximum power generation is connected. In this way, the value of the maximum generated current can be obtained at an early stage. In the explanation below, MPPT control is assumed to be performed on a priority basis on the DC/DC converter 11-1.

For example, when the maximum power generation of the power generation apparatus 10-1 is 100 W, the maximum power generation of the power generation apparatus 10-2 is 200 W, the maximum power generation of the power generation apparatus 10-3 is 300 W, and the power consumption of the AC input devices 3 is 200 W, then the controller 14 performs MPPT control on the DC/DC converter 11-1 and obtains 100 W from the power generation apparatus 10-1. For the remaining 100 W, the controller 14 may perform control to subject the DC/DC converters 11-2 and 11-3 to load following control so that the total power obtained from the power generation apparatus 10-2 and the power generation apparatus 10-3 is 100 W, or the controller 14 may perform control to subject only one of the DC/DC converters 11-2 and 11-3 to load following control so as to obtain 100 W from only one of the power generation apparatuses 10-2 and 10-3.

Next, the remaining power generation capability calculator 148 obtains the value of the generated current I1 _(M) of the power generation apparatus 10-1 from the input current sensor 20-1 (step S104). Using the generated current I1 _(M) of the power generation apparatus 10-1, the remaining power generation capability calculator 148 then calculates the remaining power generation capability of the remaining power generation apparatuses 10-2 and 10-3 as the difference between the maximum power generation and the present power generation (step S105).

The remaining power generation capability calculator 148 stores the values of the generated voltage V2 _(M) and V3 _(M) of the power generation apparatuses 10-2 and 10-3 during interconnected operation (i.e. during MPPT control) and calculates the maximum power generation P2 _(M) of the power generation apparatus 10-2 as I1 _(M)×V2 _(M) and the maximum power generation P3 _(M) of the power generation apparatus 10-3 as I1 _(M)×V3 _(M). For example, when the DC/DC converter 11-2 is subjected to load following control as illustrated in FIG. 6, the remaining power generation capability calculator 148 calculates the remaining power generation capability of the power generation apparatus 10-2 as P2 _(M)−(I2 _(L)×V2 _(L)). The remaining power generation capability calculator 148 acquires the current I2 _(L) from the input current sensor 20-2 and acquires the voltage V2 _(L) from the input voltage sensor 19-2. Using the generated current I1 _(M) of the power generation apparatus 10-1, the remaining power generation capability calculator 148 thus calculates the remaining power generation capability of the other power generation apparatuses 10-2 and 10-3.

Thus far, the case of considering the amount of sunlight to be the same between the power generation apparatuses 10 has been described. The amount of sunlight may differ between power generation apparatuses 10, however, such as in the case of installing the power generation apparatuses 10 to face different directions on a hip roof.

FIGS. 8A and 8B illustrate the power generation amount when the amount of sunlight differs between the power generation apparatuses 10. When the power generation apparatus 10-1 is installed on the west side of the roof, the power generation apparatus 10-2 is installed on the east side of the roof, and the power generation apparatus 10-3 is installed on the south side of the roof, the values of the respective generated currents I1 _(M), I2 _(M), and I3 _(M) differ during interconnected operation. The values of the generated currents I1 _(M), I2 _(M), and I3 _(M) also vary in accordance with the amount of sunlight. FIG. 8A illustrates the maximum power generation in the case of a large amount of sunlight at 10 AM, whereas FIG. 8B illustrates the maximum power generation in the case of a small amount of sunlight at 10 AM.

The difference in the amount of sunlight is determined by the direction of the sun. Therefore, when the amount of sunlight on each power generation apparatus 10 differs, the remaining power generation capability calculator 148 stores the ratio of the maximum power generation or generated current of each power generation apparatus 10 during interconnected operation along with time information.

During interconnected operation (during MPPT control), the remaining power generation capability calculator 148 stores the ratio of the maximum power generation P1 _(M), P2 _(M), and P3 _(M) of the power generation apparatuses 10 or the ratio of the maximum generated current I1 _(M), I2 _(M), and I3 _(M) of the power generation apparatuses 10. During independent operation, the remaining power generation capability is calculated based on the stored maximum power generation ratio or maximum generated current ratio.

When calculating the remaining power generation capability based on the maximum power generation ratio, then based on the value of the generated current I1 _(M) of the power generation apparatus 10-1 acquired from the input current sensor 20-1 and the value of the generated voltage V1 _(M) acquired from the input voltage sensor 19-1, the remaining power generation capability calculator 148 calculates the maximum power generation P1 _(M) as I1 _(M)×V1 _(M) and calculates the maximum power generation P2 _(M) and P3 _(M) based on the maximum power generation ratio.

When calculating the remaining power generation capability based on the maximum generated current ratio, the remaining power generation capability calculator 148 acquires the value of the generated current I1 _(M) of the power generation apparatus 10-1 from the input current sensor 20-1, calculates the maximum generated currents I2 _(M) and I3 _(M) based on the maximum generated current ratio, calculates the maximum power generation P2 _(M) as I1 _(M)×V2 _(M), and calculates the maximum power generation P3 _(M) as I1 _(M)×V3 _(M). Once the maximum power generation is known, the difference from the actual power generation is calculated as the remaining power generation capability.

FIGS. 9A and 9B illustrate an example of the remaining power information that the power management apparatus 2 outputs during independent operation. Here, an example of the remaining power information is illustrated for the case of the power conversion apparatus 1 performing MPPT control on the DC/DC converter 11-1, performing load following control on the DC/DC converter 11-2, and performing control so that the DC/DC converter 11-3 does not output power. In these figures, “A” represents the remaining power information of the power generation apparatus 10-1, which is connected to the DC/DC converter 11-1, in MPPT mode; “B” represents the remaining power information of the power generation apparatus 10-2, which is connected to the DC/DC converter 11-2, in load following mode; and “C” represents the remaining power information of the power generation apparatus 10-3, which is connected to the DC/DC converter 11-3.

The output interface 23 can cause the display 24 to output the power generation and the remaining power generation capability of each power generation apparatus 10 either as a bar chart that represents the composition ratio of the power generation and the remaining power generation capability with respect to the maximum power generation of each power generation apparatus 10, as illustrated in FIG. 9A, or as a pie chart that represents the composition ratio of the power generation and the remaining power generation capability with respect to the maximum power generation of each power generation apparatus 10, as illustrated in FIG. 9B. Since the power generation apparatus 10-1 in MPPT mode outputs the maximum power generation, the composition ratio of the power generation with respect to the maximum power generation is 100%.

In order to distinguish between the remaining power generation capability and the power generation, the output interface 23 causes the display 24 to output the power generation in a different form from the remaining power generation capability. In FIGS. 9A and 9B, the power generation is indicated with hatching, whereas the remaining power generation capability is indicated without hatching. The two are not limited to being distinguished between by hatching, however, and may be distinguished between in other ways, such as with different colors.

As illustrated in FIGS. 9A and 9B, the output interface 23 preferably causes the area of the bar chart and the pie chart to be proportional to the magnitude of the maximum power generation when each power generation apparatus 10 is caused to operate by MPPT control, thus allowing the remaining power generation capability to be visually grasped instantaneously. For example, when the maximum power generation of the power generation apparatuses 10-1, 10-2, and 10-3 is respectively 100 W, 200 W, and 300 W, the areas of the bar charts and pie charts are set to a ratio of 1:2:3. In the case of displaying the remaining power information as a bar chart, the length of each bar chart is preferably set to be the same, and the width of each bar chart is preferably varied according to the maximum power generation, as illustrated in FIG. 9A. By aligning the height of each bar chart, a common scale can be used when displaying the proportion of the generated power with respect to the maximum power generation in the length direction, thereby improving visibility. The output interface 23 may also display the value of the remaining power generation capability along with the bar chart or the pie chart or may provide audio notification of the value of the remaining power generation capability.

In this way, the power management apparatus 2 according to this disclosure receives remaining power information regarding remaining power generation capability of the power generation apparatus 10 from the power conversion apparatus 1 via the communication interface 22 and outputs the remaining power information via the output interface 23. Therefore, the power management apparatus 2 can report the remaining power information, and the user can accurately learn the remaining power information.

The above embodiments have been described as representative examples, but it is to be noted that many modifications and substitutions within the scope and spirit of this disclosure will be apparent to a person of ordinary skill in the art. Accordingly, this disclosure should not be considered to be limited by the above-described embodiments but rather may be modified or altered in a variety of ways without deviating from the scope of the patent claims.

For example, even when using a plurality of wind power generators as power generation apparatuses, the power management apparatus may receive remaining power information from the power conversion apparatus and output the remaining power information. Furthermore, since there is no remaining power generation capability for the power generation apparatus operating under MPPT control, the power management apparatus may cause the remaining power information of only power generation apparatuses other than the power generation apparatus operating under MPPT control to be displayed.

REFERENCE SIGNS LIST

-   1 Power conversion apparatus -   2 Power management apparatus -   3 AC input device -   4 DC input device -   10 Power generation apparatus -   11 DC/DC converter -   12 Intermediate link capacitor -   13 Inverter -   14 Controller -   15 Communication interface -   16 DC/DC converter -   18 Switching element -   19 Input voltage sensor -   20 Input current sensor -   21 Intermediate link voltage sensor -   22 Communication interface -   23 Output interface -   24 Display -   25 Speaker -   141 Duty cycle controller -   142 Control mode determiner -   143 MPPT controller -   144 Load following controller -   145 Input voltage controller -   146 Clock generator -   147 PWM unit -   148 Remaining power generation capability calculator 

The invention claimed is:
 1. A power management apparatus for communicating with a power conversion apparatus configured to detect a power outage and perform an independent operation in response to the power outage, the power management apparatus comprising: a communication interface configured to acquire remaining power information regarding a remaining power generation capability of a power generation apparatus from the power conversion apparatus during the independent operation, wherein the remaining power generation capability is a difference between a maximum power generation and a present power generation; and an output interface configured to cause the remaining power generation capability of the power generation apparatus in a load following mode to be output graphically, power generation being controlled to follow load power in the load following mode.
 2. The power management apparatus of claim 1, wherein the output interface causes power generation of the power generation apparatus in the load following mode to be output graphically in a different form from the remaining power generation capability.
 3. The power management apparatus of claim 2, wherein the output interface causes the power generation and the remaining power generation capability of the power generation apparatus in the load following mode to be output graphically as a bar chart or a pie chart representing a composition ratio of the power generation and the remaining power generation capability with respect to maximum power generation.
 4. The power management apparatus of claim 3, wherein the output interface causes power generation of a power generation apparatus in MPPT mode to be output graphically as a bar chart or a pie chart in which a composition ratio of the power generation with respect to the maximum power generation is 100%, the power generation being controlled to follow a maximum power point in the MPPT mode.
 5. The power management apparatus of claim 3, wherein the output interface causes an area of the bar chart or the pie chart to be proportional to a magnitude of the maximum power generation.
 6. The power management apparatus of claim 1, wherein the communication interface receives the remaining power information from a power conversion apparatus in communication with the power management apparatus when the power conversion apparatus performs independent operation that is disconnected from a power grid.
 7. The power management apparatus of claim 1, wherein a plurality of power generation apparatuses are connected in parallel to a power conversion apparatus in communication with the power management apparatus, and the output interface causes remaining power generation capability of the plurality of power generation apparatuses in the load following mode to be output graphically.
 8. The power management apparatus of claim 7, wherein the output interface causes power generation and remaining power generation capability of one of the plurality of power generation apparatuses in the load following mode to be output graphically in different forms.
 9. The power management apparatus of claim 8, wherein when graphically outputting the remaining power generation capability of the plurality of power generation apparatuses as a bar chart, the output interface sets a length of each bar chart to be equivalent and varies a width of each bar chart according to output.
 10. The power management apparatus of claim 7, wherein each of the plurality of power generation apparatuses connected to the power conversion apparatus is a solar cell string in which a plurality of solar cell modules are connected in series.
 11. The power management apparatus of claim 1, wherein the power management apparatus is capable of communicating with a power conversion apparatus for converting power of the power generation apparatus.
 12. The power management apparatus of claim 10, wherein all of the plurality of solar cell modules have equivalent characteristics.
 13. A power management system comprising: a power conversion apparatus for converting power of a power generation apparatus and supplying the power to a load of a consumer's facility; and a power management apparatus capable of communicating with the power conversion apparatus, wherein the power conversion apparatus is configured to detect a power outage and perform an independent operation in response to the power outage, and the power conversion apparatus comprises: a controller configured to acquire remaining power information regarding a remaining power generation capability of the power generation apparatus during the independent operation, wherein the remaining power generation capability is a difference between a maximum power generation and a present power generation; and a first communication interface configured to transmit remaining power information to the power management apparatus, and the power management apparatus comprises: a second communication interface configured to receive remaining power information from the power conversion apparatus during the independent operation; and an output interface configured to cause the remaining power generation capability of the power generation apparatus in a load following mode to be output graphically, power generation being controlled to follow load power in the load following mode.
 14. A method for managing power by communicating with a power conversion apparatus configured to detect a power outage and performing an independent operation in response to the power outage, the method comprising: acquiring remaining power information regarding a remaining power generation capability of a power generation apparatus from the power conversion apparatus during the independent operation, wherein the remaining power generation capability is a difference between a maximum power generation and a present power generation; and causing the remaining power generation capability of the power generation apparatus in a load following mode to be output graphically, power generation being controlled to follow load power in the load following mode. 